Thermal SiO observations of a shell attached to
the nonthermal filaments in Sgr A

Handa Toshihiro1, Tsuboi Masato2,
Sakano Masaaki3

1 Institute of Astronomy, University of Tokyo
2 Ibaraki University
3 University of Leicester

E-mail contact: handa@ioa.s.u-tokyo.ac.jp

The CS observations with NRO 45m telescope reveals that a dense
molecular shell is located between
Sgr A and the non-thermal filament of radio arc,
and that the shell shows an interacting
feature with the non-thermal filament (Tsuboi, Ukita and Handa, 1997).
Using NRO 45m telescope
we observed the shell in SiO (J=1-0, v=0) and SiO
(J=2-1, v=0),
which are thermally excited
lines and thought to be an interstellar shock indicator.

Features associated with the shell are clearly appeared
in both the SiO lines.
All features associated with the shell are similar to
those in the CS line in l-b-v 3-dimensional
space. Intensity ratio of
SiO (J=1-0) to CS (J=1-0) is ~0.24,
using an intensity correlation diagram.
Similarity between the CS and SiO features directly means X-ray
features observed with ASCA and Chandra are also associated with the shell.

Intensity ratio of two SiO lines (J=2-1 over
J=1-0) shows
rather uniform over the shell, suggesting the shell is uniform in density.
We estimated the averaged value of the ratio is ~0.9,
using an intensity correlation diagram.